Expect it to take about 1-1/2 hours to get there. You can spend anywhere from 40 minutes to a full day at the Cliffs.
There are a lot of things you can add to your daytrip based on your interests. You could swing through part of the Burren on the way home...or one of my favorite easy stops on the way would be Quin Abbey.
Made that trip last week -- easy and interesting as you wind your way through the Burren. New visitors center at Cliffs is interesting and worthwhile, and new path makes it easy to get to the top. Parking a bit strange -- too far away for me -- but nonetheless a nice addition. You will enjoy for sure!
You have no idea how much work piles up till you have been out of the country for over a month! We will look forward to hearing about your trip when your desk has been cleared off.